urandomb.c
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上传日期:2022-08-06
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- /* mpf_urandomb (rop, state, nbits) -- Generate a uniform pseudorandom
- real number between 0 (inclusive) and 1 (exclusive) of size NBITS,
- using STATE as the random state previously initialized by a call to
- gmp_randinit().
- Copyright 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
- This file is part of the GNU MP Library.
- The GNU MP Library is free software; you can redistribute it and/or modify
- it under the terms of the GNU Lesser General Public License as published by
- the Free Software Foundation; either version 3 of the License, or (at your
- option) any later version.
- The GNU MP Library is distributed in the hope that it will be useful, but
- WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
- License for more details.
- You should have received a copy of the GNU Lesser General Public License
- along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */
- #include "gmp.h"
- #include "gmp-impl.h"
- void
- mpf_urandomb (mpf_t rop, gmp_randstate_t rstate, mp_bitcnt_t nbits)
- {
- mp_ptr rp;
- mp_size_t nlimbs;
- mp_exp_t exp;
- mp_size_t prec;
- rp = PTR (rop);
- nlimbs = BITS_TO_LIMBS (nbits);
- prec = PREC (rop);
- if (nlimbs > prec + 1 || nlimbs == 0)
- {
- nlimbs = prec + 1;
- nbits = nlimbs * GMP_NUMB_BITS;
- }
- _gmp_rand (rp, rstate, nbits);
- /* If nbits isn't a multiple of GMP_NUMB_BITS, shift up. */
- if (nbits % GMP_NUMB_BITS != 0)
- mpn_lshift (rp, rp, nlimbs, GMP_NUMB_BITS - nbits % GMP_NUMB_BITS);
- exp = 0;
- while (nlimbs != 0 && rp[nlimbs - 1] == 0)
- {
- nlimbs--;
- exp--;
- }
- EXP (rop) = exp;
- SIZ (rop) = nlimbs;
- }